Method of investing patterns for dental pieces



D. N. BRADLEY. .JR

ECES

Filed May 22, 1935 2 Shests-S1eet l May 26, 19%.,

I METHOD OF INVESTING PATTERNS FOR DENTAL P May 26, 1936- D. N. BRADLEY. JR 2,042,330

METHOD OF INVESTING PATTERNSFOR DENTAL PIECES Filed May 22, 1935 2 Sheets-Sheet 2 Patented May 26, 1936 PATENT vOFFICE METHOD F INVESTING PATTERNS FOR DENTAL PIECES David N. Bradley, Jr., Joliet, Ill., assignor of onehalf to William B.. Andrews, Chicago, Ill.

Application May 22, 1933, Serial No. v672,184? 3 Claims. (Cl. :Z2-190.1)

'Ihe present invention has reference to a method of applying investment material to wax patterns for inlays, crowns, bridge attachments, clasps, bridge pontics, partial or full dentures and other dental pieces.

Heretofore, t has been customary in connection with the casting of dental pieces to apply the investment material to the Wax patterns for the pieces either by painting a coating of the material on the patterns by way of a brush and while the patterns are mounted on sprue farmers and then positioning the coated patterns in casting rings and pouring additional investment material into the rings and around the patterns or by placing the Wax patterns on sprue formers and in casting rings and mounting the rings ona vibrating mechanism and then pouring the investment material into the rings while the latter are vibrated by the mechanism. In practice it has been found that both of these methods of applying investment material to wax patterns are defective in that they do not contemplate the elimination of air bubbles or trapped air around the wax patterns and as a result, the castings which are made from the patterns are imperfect and do not seat or t properly. When the investment material is applied to the wax patterns by way of a brush, it has been found that the patterns are sometimes distorted as the result of contact with the bristles of the brush, especially in instances where the patterns are made of comparatively soft wax and that air is sometimesv trapped in the crevices into which the brush cannot penetrate. When the material is applied to the patterns by way of a vibrating mechanism, air bubbles and trapped air are often encountered on the under faces of the patterns because the investment material will not iow readily into the various irregular surfaces and crevices at the bottom parts of the patterns. 'Ihe primary object ofthe present'invention is to provide an improved method of applying investment material to wax patterns for` inlays, crowns, bridge attachments and pontics, clasps, dentures and other dental pieces which effectively eliminates distortion of the patterns as well as the formation of air bubbles or trapping of air on the patterns. In general this method comprehends first placing the pattern to be invested on a sprue former and then inserting the pattern into a well or other'receptacle having a mist of water therein, in order to moisten all portions of the pattern.

After insertion-of the pattern into the well investment material in powdered form is jetted by around the pattern. The powdered investment l material, upon striking the mist, becomes semiliquid and coats the pattern in such a manner that the latter is in no way distorted and is entirely free from air bubbles and trapped air in the crevices or irregular external surfaces.

Anotherobject of the invention is to provide a method of investing patterns for dental pieces which is less tedious and results in better castings than methods which have heretofore been employed.

Other objects of the invention and the various advantages and characteristics of the present method will be apparent from a consideration of the following detailed description.

The invention consists in the several novel features which are hereinafter set forth and are more particularly defined by claims at the conclusion hereof.

In the drawings which accompany and form a part of this specification 'or disclosure and in 'which like numerals of reference denote corresponding parts throughout the several views:

Figure 1 is a vertical longitudinal section of an apparatus for carrying out the improved method;

Figure 2 is an enlarged sectional view of the well of theapparatus, illustrating in detail the means for forming a mist therein;

Figure 3 is a perspective of the well, exhibiting the manner in which the powdered investment material is jetted into the mist in the well for pattern-investing purposes;

Figure 4 is a plan view of the well; and

Figure 5 is a section on the line 5--5 of Figure 1.

The improved method of applying investment material to wax patterns for inlays, crowns, bridge attachments and pontics, clasps, partial or full dentures and other dental pieces, is adaptedv to be carried out in an apparatus of the type shown in the drawings. This apparatus comprises a well lil. For purposes of illustration, a wax pattern P for an inlay is shown in connection with the apparatus. Thewell I0 is adapted to have the pattern P disposed therein for purposes of investment material application and consists of'a cylindrical side wall II and a circular bottom4 I2. A jacket I3 surrounds the well and holds the latter in an elevated position. 'Ihis jacket comprises a cylindrical side wall I4 and a bottom wall I5. 'I'he side wall I4 surrounds the side wall II of the well I0 and is spaced from the latter as shown in the drawings. In addition to the side wall I4 and the shaped top 'I6 and a partition Il. The partition extends horizontally across the central portion of the side wall Il and serves to support the well I 0 and to vdivide the jacket into an upper chamber I8 anda lower chamber I9. The ring-shaped top I5 extends between and is secured to thev upper edges of the side walls of the well in the jacket and closes the upper compartment I8. The latter is connected by a hose 20 to receive air under pressure from any suitable source of supply. The hose 20, as shown in the drawings, is connected to a nipple 2| on the side wall I4 of the jacket I3 and includes a valve 2li whereby the supply of compressed air to the chamber I 8 may be controlled. 'I'he lower chamber I9 is adapted toretain a column of water and extends under the well I0. The jacket is extended at one side theref to form a laterally extending leg 22 for the chamber I9. This leg embodies at the top thereof a cross wall 23 which has an opening 24 whereby water may be introduced into the chamber I9. A'

plug 25 ts removably in the opening 24 and serves normally to close thelatter.

The water in the lower chamber I9 is adapted to be formed into mist in the well I0 and for this purpose vertically extending tubes 26 are provided. These tubes, as shown particularly in Figure 2 of the drawings, extend through the partition I1 and the bottom I2 of the well and are arranged in an annular series around the side wall II of the well. The lower ends of the tubes are spaced upwardlya slight distanceL from the bottom wall I5 of the jacket so that water from the chamber I9 may flow into the tubes. I'he upper ends of the tubes extend alongside of the side wall II of the well. They terminate at different elevations and are associated with jets 21. These jets are secured to and extend linwardly from the side wall II of the well and receive air under pressure from the upper chamber I8 in the jacket I3. They are arranged so as to direct streams of air across the upper ends of the tubes 28 and, as shown in the drawings, extend .at different angles. The streams of' air emanating from the jets operate to draw water from the lower chamber I9 in the jacket I3 upwardly through the tubes 28 and disperse the water in mist form in the well III. By terminating the upper ends of the tubes at dliferent elevations and having the jets 21 extend`at different angles, a water mist is formed substantially throughout the entire well. The intensity of the mist in the well may becomtrolled by adjusting the valve 20* and thus controlling the amount of air under-pressure that is supplied to or delivered into the chamber I8. 'I'he tubes 28 and the jets 21 exemplify simple means for forming a water mist in the well I0.

It is contemplated that investment material in powdered form be jetted into the mist in the well by air lmder pressure and for this purpose the apparatus includes a letting device 2l. This device includes a bin 2l and a nozzle I0. The bin is adapted to be filled with a supply of the POW- dered investment material and Aembodies a cross wallil which serves as a bottom for the supply of investment material and forms an air compartment 32 in the bottom of the bin. The cross j wall 3| extends upwardly and outwardly at the marginal part thereof so that the material tends v to work towards the center, and the center of 3i' and is driven'by an electric motor 58 at one side of the bin 29 through the medium of a speed reducing gearing I1. Air under pressure isde-4 livered into the compartmentv 32 by a hose 38 which embodies a control valve 39 and is con- 5 nected to any suitable source of air supply. The compartment communicates`with theiinozzle 30 by way of a mouthpiece 40' and a hose 4I. The mouthpiece is located in the compartment 32 beneath the cross wall lI and is arranged eso as to receive the investment material which is discharged from the bin by the screw conveyor 34. 'Ihe hose II extends between the mouthpiece 40 and the nozzle III and permits the nozzle to be manipulated by hand over the well III.- When the motor It is driven'so as to actuate the screw conveyor Il and the valve I0 is opened so as to permit air under pressure to flow into the compartment 32, the material discharged from the screw conveyor is picked up by the air travelling through the chamber 32- and is'carried via the hose 4I through the mouthpiece 40 to the nozzle l0. .By manipulating the nozzle 30, the powdered investment material may be directed into the well III for contact with the mist which is produced 25 by the tubes and the jets 21.

` When the apparatus is to be used to apply a coating of investment material to the wax pattern P, the valve 2l is'rst opened so as to cause air*y under pressure to ow into the chamber Il and through the jets o21. The streams of air under pressure emanating from the jets 21 flow across the upper ends of the tubes 25 and draw water from the chamber Il through the tubes and disperse it in mist form in the well. After vforma tion ofthe mist in' the well, the wax patterns P are mounted on sprue formers and positioned in' the well, .as shown in Figure'l ot the drawings. While theC pattern is so positioned. the device 2l' is started by opening the valve and starting 4o the electric motor 36 and the nomle l0 is manipufy lated so that the powdered investment material discharged therefrom is directedv in tothe well andagainstthepattern. Assoonasthepowdered investment material strikes the mist and thepat- 45 tern, it'beeomes semi-liquid and coats the pattern. By manipulating the nomle Il and the wax pattern, the pattern may be'coated completely with investment material. When the devicev 2l is in operation. the investment material 50 is discharged from' the bin into the mouthpiece A40 by means of thescrew conveyor $4 and is carriedby the air under pressure flowing through thechamber llthroughtbeho'se .Il tothe nozzle 30, as previously pointedvout. A`By immersing or 55 positioningthewaxpattemPin awatermistand spraying onjettingtbe investment materialdn powdered form into the milt and against the. pattern, thecoating whichv is termed around the pattern isentirely freefr'omairbubbles and there 00 isnolikelihoodwhatsoeverotairb'eingtrapped inthecrevices..mrtbermore.tbepatternisin noy way distorted and as a result...produces.a

- perfect and smooth casting.. After coating with the mvesmept wenn in the wen le, the pstternisplacedinacastingringand issurrounded with'additional investment material. Thereafter, the sprue former iswithdrawn, the pattern melted k out and.V molten metal pom'ed into the-cavity as well understood in the art. intensity of the mist in the well may be controlledjas previously pointed out, by regulating the valve 2| and the jetting ofthe powdered investment material from the nozzle 3l may be controlled by adjusting the 75 bubbles which would result in a valve 39 and controlling the speed of the electric motor 36 for driving the screw conveyor 34.

'I'he well I0 is drained by means of a pipe 42 which leads from the bottom I2 of the well and out through the jacket I3. l

The method as can'ied out or. -practiced with the hereinbefore described apparatus results in the wax pattern being evenly coated with the investment material and entirely eleminates distortion of the pattern and the formation of air faulty casting and an imperfect ilt of the piece.

Whereas the method has been described in connection with the investment of a wax pattern, it is to be understood that it may be used to coat with investment material impressions for models or casts or plasters and other forms of dental pieces. It is also to be understood that the invention is not restricted to the details set forth, since these may be modified within the scope of the appended claims, without departing from the spirit and scope of the invention.

Having thus described the invention, what I claim as new and desire to secure by Letters Patent, is:

1. That improvement in investing a destructible pattern for an inlay or other dental piece which consists in mounting the pattern on a sprue former, then delivering water in atomized form around the pattern while the latter .is on the sprue former and at the same time jetting with air under pressure and from diierent angles powdered investment material into the water and against the pattern in order completely to coat' the latter with the material, then placing the sprue former and coated pattern in a casting ring and inally iling the ring with moist investment material in orderl to complete the investment of 5 the pattern.

- 2. That improvement in investing a destructible pattern for an inlay or other dental piece whichconsists in mounting the pattern on a sprue former, then delivering water in atomized iorm 10 around the pattern while the latter is on the sprue former and at the same time lietting powdered investment material from diilerent angles into the water and against all portions oi the pattern l in order to apply a preliminary coating ci the 15 y' material entirely around the pattern, then placing the sprue former and coated pattern in a casting ring, and inally pouring moist investment material into the ring until the coated pattern is completely invested and the ring is lled. 20

3. That improvement in investing a destructible pattern for an inlay or other dental piece which consists in mounting the pattern on one end of a sprue former, then forming a mist around the pattern while the latter is on the sprue 25 former and simultaneously delivering powdered investment material into the mist from diierent angles so as completely tc coat the pattern, then placing the sprue former and coated pattern in a'casting ring, and inally pouring moist invest- 30 ment material into the-ring until the coated pattern is completely covered and the ring is filled. DAVID N. BRADLEY, Jn. 

